The need for measuring the relative speed between a fluid and an object arises in a substantial number of environments. For example, the relative speed of a fluid through a pipe is often of significant importance in manufacturing processes and the like. By way of further example, the relative speed of an object such as a vehicle or vessel through a fluid such as air or water is often of interest. Thus, aircraft traveling through the air and watercraft traveling through or upon the water create a need for measurement of the speed of the aircraft or watercraft relative to the air or water in which they move.
To meet the need for measuring relative speed between a fluid and a reference, practitioners in the art have created a variety of systems and apparatus. Most such system utilize some element which engages the fluid of interest and which is acted upon by the fluid due to its relative motion.
In a common type of relative speed measurement, aircraft often employ a capture tube and pressure gage combination to measure aircraft speed relative to the air through which they are traveling. Also, many systems used in aircraft and watercraft provide a rotatable propeller or the like which engages the air or water within the environment and which is rotated thereby during motion.
While the various types of fluid-engaging measurement systems heretofore provided have, to some extent, functioned satisfactorily and have, in some instances, enjoyed commercial success, there remains nonetheless a continuing need in the art for ever more improved relative speed measurement apparatus and systems which function without the need of directly engaging the fluid of interest.